Study of an Alcohol’s Influence on the CMC and Thermodynamic Functions of Anionic Surfactants in DMA/Long-chain Alcohol Solutions Using a Microcalorimetric Method

The power-time curves for the micelle formation process were determined for two anionic surfactants, sodium laurate (SLA) and sodium dodecyl sulfate (SDS), in mixed alcohol + N,N-dimethylacetamide (DMA) solvent using titration microcalorimetry. From the data of the lowest point and the area of the power-time curves, their critical micelle concentration (CMC) and ΔH _m^o were obtained. The other thermodynamic functions of the micellization process (ΔG _m^o and ΔS _m^o) were also calculated with thermodynamic equations. For both surfactants, the effects of the carbon number (chain length) of the alcohol, the concentration of alcohol, and the temperature on the CMC and thermodynamic functions are discussed. For systems containing identical concentrations of a different alcohol, values of the CMC, ΔH _m^o and ΔS _m^o increased whereas ΔG _m^o decreased with increasing temperature. For systems containing an identical alcohol concentration at the same temperature, values of the CMC, ΔH _m^o,ΔG _m^o and ΔS _m^o decrease with increasing carbon number of alcohol. For systems containing the same alcohol at the same temperature, the CMC and ΔG _m^o values increase whereas ΔH _m^o and ΔS _m^o decrease with increasing alcohol concentration.     

Studies on the CMC and Thermodynamic Functions of a Cationic Surfactant in DMF/Long-Chain Alcohol Systems Using a Microcalorimetric Method

The power-time curves of the micelle formation process were determined at four temperatures for a cationic surfactant [cetyltrimethylammonium bromide (CTAB)] in a non-aqueous solvent [N,N-dimethylformamide (DMF)] by titration microcalorimetry. From the data of the minimum of the titration point and the area of the power-time curves, values of their CMC and ΔH _m ^θ were obtained. Values of ΔG _m ^θ and ΔS _m ^θ were also calculated according to standard thermodynamic relations. For the cationic surfactant CTAB, the relationships involving the carbon numbers of the alcohols, the alcohol’s concentration, and the temperature on the CMC, and also the thermodynamic functions for micellization are discussed. For systems containing an identical concentration of various alcohols, values of the CMC, ΔH _m ^θ and ΔS _m ^θ increased whereas those of ΔG _m ^θ decreased with increasing temperature. For systems containing identical alcohol concentrations at the same constant temperature, values of the CMC, ΔH _m ^θ ,ΔG _m ^θ and ΔS _m ^θ decreased with increasing carbon number of the alcohol. For systems containing the same alcohol at the same temperature, the CMC and ΔG _m ^θ values increased whereas ΔH _m ^θ and ΔS _m ^θ decreased with increasing alcohol concentration.     

Interfacial and Thermodynamic Properties of Anionic‐Nonionic Mixed Surfactant System: Influence of Hydrophobic Chain Length of the Nonionic Surfactant

The influence of hydrophobic chain length in nonionic surfactants on interfacial and thermodynamics properties of a binary anionic‐nonionic mixed surfactant was investigated. In this study, nonionic surfactants lauric‐monoethanolamide (C₁₂ MEA) and myrisitic‐monoethanolamide (C₁₄ MEA) were mixed with an anionic surfactant, α‐olefin sulfonate (AOS). The critical micelle concentration (cmc), maximum surface excess (Γ_max), and minimum area per molecule (A_min) were obtained from surface tension isotherms at various temperatures. The thermodynamic parameters of micellization and adsorption were also computed. Micellar aggregation number (N_agg), micropolarity, and binding constant (K_sv) of pure and mixed surfactant system was calculated by fluorescence measurements. Rubingh's method was applied to calculate interaction parameters for the mixed surfactant systems.     

Effect of Emulsification Method on the Properties of Lecithin‐ and PGPR‐Stabilized Water‐in‐Oil‐Emulsions

Water‐in‐oil (w/o) emulsions were prepared with phosphatidylcholine‐depleted lecithin or polyglycerol polyricinoleate (PGPR) as emulsifying agents. The effect of different laboratory emulsification devices and the effect of sodium chloride on particle size distribution, coalescence stability, and water droplet sedimentation were investigated. The properties of lecithin‐stabilized w/o emulsions were found to depend more strongly on the emulsifying method than those prepared with PGPR. The rotor‐stator system was not suitable for preparing stable w/o emulsions with lecithin. Whereas the addition of salt was essential to achieve coalescence‐stable emulsions prepared with PGPR, the presence of NaCl favored the coalescence of water droplets and phase separation in emulsions containing lecithin.     

Synthesis of Polyvinylacetate‐Sodium Montmorillonite Hybrids by Emulsion Polymerization in the Presence of Anionic Surfactants

The emulsion polymerisation of vinyl acetate (VAc) in presence of sodium dodecylsulphate (SDS) and sodium montmorillonite (NaMMT) is used in order to achieve polymer‐clay hybrids. The influence of the polyvinylacetate (PVAc), SDS, and PVAc‐SDS complex on the NaMMT structure also was investigated. The VAc emulsion polymerization rate exhibits a maximum as the NaMMT concentration increases. The XRD patterns correspond to hybrids with intercalated structure. If a water soluble comonomer, ammonium sulphato ethylmethacrylate (ASEMA) is used for copolymerization with VAc, a exfoliated hybrid structure (from XRD spectra) is obtained. The solid materials were analysed by TGA, FTIR, XRD, SEM, and TEM.     

Effects of Short‐Chain Alcohol on the Micellization of Gemini Surfactant C16‐6‐16 · 2Br in Aqueous Solution

The effects of ethanol, n‐butanol, and n‐hexanol on the micellization of cationic Gemini surfactant C16‐6‐16 · 2Br have been investigated using conductance and steady fluorescence measurements. The results show that the critical micelle concentration (CMC) increases with the addition of ethanol, but decreases with n‐butano1 or n‐hexanol. With the addition of the above alcohols, both the micelle ionization degree and the mole fraction of alcohol in the micelle increase, however, the micelle aggregation number decreases at a fixed concentration of surfactant. When given a special concentration of alcohol, the micelle aggregation number increases as the increase of the surfactant concentration.     

Facile and Efficient Method for the Prins Reactions of Styrenes and Homoallyl Alcohols to 1,3‐Dioxanes and 4‐Tetrahydropyranols Using Bismuth(III) Triflate

Abstract

Bismuth(III) triflate has been found to be an efficient catalyst for the Prins reactions of styrenes and homoallyl alcohols, the reaction proceeds rapidly and affords the corresponding 1,3‐dioxanes and tetrahydropyran‐4‐ol in good yields. Scope and limitations of the styrenes and homoallyl alcohols are reported.     

The Effects of Salts and Ionic Surfactants on the Micellar Structure of Tri‐Block Copolymer PEO‐PPO‐PEO in Aqueous Solution

The micelles of two poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) block copolymers, P123 and F127 (same mol wt of PPO but different % PEO) in aqueous solution in the absence and presence of salts as well as ionic surfactants were mainly examined by dynamic light scattering (DLS). The study is further supported by cloud point and viscosity measurements. The change in cloud point (CP), as well as the size of micelles in aqueous solution in presence of salts obeys the Hofmeister lyotropic series. Addition of both cationic cetylpyridinium chloride (CPC) and anionic sodium dodecylsulfate (SDS) surfactants in the aqueous solution of P123 show initial decrease of micellar size from 20 nm to nearly 7 nm and then increasing with a double relaxation mode, further in the presence of NaCl this double relaxation mode vanishes. The effect of surfactant on F127, which has much bigger hydrophilic part is different than P123 and have no double relaxation. The relaxation time distributions is obtained using the Laplace inversion routine REPES. Two relaxation modes for P123 are explained on the bases of Pluronic rich mixed micelles containing ionic surfactants and the other smaller, predominantly surfactant rich micelles domains.     

Effect of Particle Properties on the Break Up of Nanoparticle Clusters Using an In‐Line Rotor‐Stator

This study was carried out to investigate the break up of nanoparticle clusters in a liquid using an in‐line rotor stator. Two types of fumed silica particles were dispersed in distilled water: Aerosil 200 V, which is hydrophilic, has a primary particle size of 12 nm and Aerosil R816 which is based on Aerosil 200 V and surface modified to render it hydrophobic. The article reports on the rheology of the dispersions, particle size analysis, the effect of concentration, and processing conditions such as the rotor speed, that is, the specific power input, and flow rate, that is, the residence time.     

Manifestation of the Even–Odd Effect in the Spectral Properties of Solvated Electron and in the Probability of Positronium Formation in Alcohols

A change in the energy E _max of the solvated electron, which corresponds to the maximum intensity of its optical absorption spectrum in the homologous series of alcohols seems to be alternating in character. The effect is retained upon elevation of pressure up to 2 kbar but disappears in alcohols frozen at 77 K. Probably, the effect also holds for amines. The alternating character of variation is also observed for the intensity Y ₁ of the narrow components of the angular spectrum of -photons generated upon positron annihilation in alcohols and normal alkanes. The nature of alternation of E _max is associated with the mutual elimination of electric fields induced by the dipole moments of two neighboring CH₂ groups in each solvent molecule, including also the molecules forming the solvation shell of an excess electron. That fact that the E _max value correlates to Y ₁ led to the conclusion that Y ₁, rather than the intensity I ₃ of the long-lived component of the annihilation time spectrum generally used for the purpose, more adequately characterizes the positronium formation probability.     

Efficient Transition‐Metal‐Free Oxidation of Benzylic and Secondary Alcohols to the Carbonyl Compounds Using an N‐Bromosuccinimide/NH4Cl System

The oxidation of a variety of benzylic and secondary alcohols was achieved in excellent yields using an NBS/NH₄Cl system in aqueous acetonitrile (CH₃CN‐H₂O; 7/3 v/v) at 80°C under very mild conditions.     

Anticipation on the Development of Polycarbonate Production Technology by Using Ester-interchange Method in China

Polycarbonate (hereinafter referred to as “ PC ”) is the sole product having good transparency among the 5 major engineering plastics. In 2000, the worldwide PC production capacity was reached up to 2,800,000 tons of several hundreds of brands of various grades. It is estimated that the global PC production capacity will exceed 3,500,000 tons in 2005. The global demand for PC was 1,900,000 tons in 2000, which will reach to 2,600,000 tons and more than 3,000,000 tons in 2003 and 2005 respe…     

Effect of Amino‐Acid‐Based Polar Oils on the Krafft Temperature and Solubilization in Ionic and Nonionic Surfactant Solutions

Abstract

The Krafft temperature and solubilization power of ionic and nonionic surfactants in aqueous solutions are strongly affected by added polar oils such as amino‐acid‐based oils (e.g., N‐acylamino acid esters, AAE), because they tend to be solubilized in the surfactant palisade layer. The Krafft temperatures of 5 wt.% sodium dodecyl sulfate (SDS)‐water and octaoxyethylene octadecyl ether (C₁₈EO₈)‐water systems largely decreases upon addition of AAE and 1‐hexanol, whereas it decreases very slightly in isopropyl myristate (IPM) and n‐dodecane. The lowering of the Krafft temperature can be explained by the same mechanism as the melting‐temperature reduction of mixing two ordinary substances. Namely, the polar oils are solubilized in the surfactant palisade layer of micelles and reduce the melting temperature of hydrated solid‐surfactant (Krafft temperature). On the other hand, non‐polar oil such as dodecane is solubilized deep inside micelles and makes an oil pool. The solubilization of non‐polar oil is enhanced by mixing surfactant with AAE due to an increase in micellar size.     

Effect of Different Salts on the Solubilities of Benzene and Diphenyl in t—Butyl Alcohol—Water Mixture and Hydrophobic Interaction

The solubilities of benzene and diphenyl in mixed solvents of t-butyl alcohol (TBA) and water with different salts have been determined at T=298.15,303.15,308.15 and 313.15K.The molar fraction of TBA [x(TBA)] in mixed solvent is 0.045,and the molality of the salts (ms) in mixed solvents are 0.000,0.250,0.500,0.750 and 1.000mol/kg ,respectively.The standard Gibbs energies of solution of benzene and diphenyl in the mixed solvents have also been calculated based on the solubility data.The effects of different salts on the hydrophobic interaction (HI) for benzene-benzene pair in the systems were discussed.     

Effect of L‐Aspartate Concentration on the Response of the Amperometric L‐Glutamate Sensor for the Measurement of L‐Glutamate and Aspartate Aminotransferase Activity in Serum

Abstract

L‐glutamate oxidase was immobilized in a photo‐cross‐linkable polymer membrane on a palladium strip electrode for the amperometric measurement of aspartate aminotransferas eactivity. The sample, serum for example, was injected into a buffered L‐aspartate and α‐ketoglutarate solution. L‐aspartate is the essential substrate and can transfer to L‐glutamate via the aspartate aminotransferase catalyzing reaction. Aspartate aminotransferase activity can be measured by determining the increasing rate of L‐glutamate. Under the optimal condition, the current increasing rate was proportional to the aspartate aminotransferase activity of the sample in the range of 8–200 U/L. The data are in good correlation (R²= 0.998) with data from a commercial aspartate aminotransferase assay kit. Good reproducibility (relative standard deviation=3.03%, n=8) was obtained from a sample with 50 U/L aspartate aminotransferase activity. The sensor is expectable to be applied in a clinical point‐of‐care diagnosis.     

Post‐chemiluminescence Method of the Determination of Loperamide Hydrochloride in Human Plasma and Pharmaceutical by Using Dichlorofluorescein as Chemiluminescence Reagent

Abstract

A post‐chemiluminescence (PCL) was observed when loperamide hydrochloride solution was injected into the reaction mixture after the finish of CL reaction of alkaline N‐Chlorosuccinimide (NCS) and dichlorofluorescein. Based on this phenomenon, a simple, sensitive and fast flow injection PCL method was established for the determination of loperamide hydrochloride. The possible mechanism for the PCL reaction was discussed via the investigation of the CL kinetic characteristics, the CL spectra, the fluorescence spectra. The PCL intensity responded linearly to the concentration of loperamide hydrochloride in the range 8.0×10^?10 to 6.0×10^?7 g · ml^?1 with a linear correlation of 0.9995. The detection limit was 4×10^?10 g · ml^?1. The relative standard deviation was 2.4% for 4.0×10^?8 g · ml^?1 loperamide hydrochloride (n=11). This method has been applied to the determination of loperamide hydrochloride in human plasma and pharmaceutical samples with satisfactory results.     

Effect of the Allyl Group in Reactions of Allyl Alcohol and Its Derivatives with ε-Caprolactam

Unlike saturated alcohols, allyl alcohol reacts with -caprolactam under considerably milder conditions. Allyl esters react with -caprolactam to give the corresponding allyl -acylaminocaproates. The yield of the latter decreases in going from formyl to acetyl and propionyl derivatives. The observed effect of the allyl group is explained in terms of possible allylic rearrangement in the transition state.     

Effect of Lead(II) Complexation on Solubility of β-PbO in Alkaline Solutions in the Presence of Certain Alcohols

Complex formation of lead(II) was studied, and the solubility of -PbO was determined by potentiometric titration in solutions containing sodium hydroxide (0.3-4 M) and a series of mono- and polyhydric alcohols. A correlation between the lead monoxide solubility and Pb(II) complex formation function was considered.     

Interfacial and Thermodynamic Properties of Formation of Water‐in‐Oil Microemulsions with Surfactants (SDS and CTAB) and Cosurfactants (n‐Alkanols C5–C9)

The interfacial and thermodynamic properties of water‐in‐oil microemulsion systems consisting of water, isopropyl myristate, n‐alkanol, and surfactant have been investigated using the method of dilution. The surfactants used were hexadecyl trimethylammonium bromide and sodium dodecylsulfate, and the cosurfactants were n‐alkanols with varying chain length from (C₅–C₉). The distribution of cosurfactant (n‐alkanol) between the interface of water and oil regions at the threshold level of stability as well as the energetics of the transfer of the cosurfactant from the oil to the interfacial region have been examined as a function of varying cosurfactant chain length (C₄–C₉) and temperature. The structural parameters (including dimension, population density and effective water pool radius) of the dispersed water droplets in the oil phase have also been evaluated and correlated with alkanol chain length.     

Temperature Effect on the Phase Behavior of the Systems Water/Sucrose Laurate/Ethoxylated‐mono‐di‐glyceride/Oil

The phase behavior of the systems water/sucrose laurate/ethoxylated mono‐di‐glyceride/oil was investigated as function of temperature and the weight ratio of EMDG in the mixed surfactants. The oils were R (+)‐limonene, isopropylmyristate, and caprylic‐capric triglyceride. This study demonstrates that the phase inversion temperature (PIT) decreases and the efficiency of the mixed surfactants (γ¯) increase as the weight ratio of the EMDG in the mixed surfactants increases. R (+)‐limonene gave lower phase inversion temperatures and higher efficiencies compared to isopropylmyristate, and caprylic‐capric triglyceride. The solubilization capacity of the system water/sucrose laurate/oil increased upon the addition of ethoxylated mono‐di‐ glyceride which stabilize the surfactant layer and increase the interfacial area.